Alright I'd like to replace the shifters on my Trek 7200. The area where my hands contact the handlebar is split in two. The inner half is the shifter, the outer half is just a foam cover over the metal bar. That outer foam moves around and tends to slide off the handle bars in the middle of my ride. I would like to replace the "cheap" shifters with "trigger" type shifters. I have zero idea what I need or what I should be looking for. I would like to keep it under 50 bucks for parts. I'm also taking suggestions as to what would be a good replacement for the troublesome foam outer ends. What level of difficulty is involved with this type of job?